1. Field of the Invention
The present invention relates generally to a device for measuring distance, and more particularly to a rangefinder.
2. Description of the Related Art
As the advancement of measurement of distance, optical rangefinder is the commonest device in distance measuring. It is easy and precisely in long distance measurement.
FIG. 1 shows a conventional optical rangefinder 2, including a case 50, a light receiver 51, a reference light source 52, a reflector 53, and a measuring light source 54. The light receiver 51 is mounted in the case 50. The reference light source 52 is mounted on the case 50 by two bolts 60 to emit reference beam L3. The reflector 53 is mounted in the case 50 to reflect the reference beam L3 to the light receiver 51. The measuring light source 54 is mounted on the case 50 by four bolts 61 to emit measuring beam L4 to an object 110. The measuring beam L4 is reflected by the object 110 and emits to the light receiver 51. The optical rangefinder 2 finds a difference between phases of the reference beam L3 and the measuring beam L4 in the light receiver 51 to obtain a distance between the object 110 and the rangefinder 2.
Such rangefinders 2 have to be calibrated in the manufacture. The way of calibration is to turn the bolts 60, 61 for adjustment of a distance between the reference light source 52 and measuring light source 54. However, it is not easy to turn the bolts 60, 61. Too tight or too loose may affect the arrangement and durability of the rangefinder 2. In other words, when the bolts 60 or 61 are too loose, it may cause the reference light source 52 and/or the measuring light source 54 shift. When the bolts 60 or 61 are too tight, it will break the reference light source 52 and/or the measuring light source 54. Consequently, it still has some places in the conventional rangefinder to be improved.